Perinatal depression is a common and serious mood disorder that increases morbidity and mortality in new mothers and results in poor infant/child outcomes. Current therapies often fail to produce recovery or are poorly tolerated and many pregnant women seek non-pharmacologic therapy or forgo treatment when non-pharmacologic options are not available. Expectant and new mothers who suffer from circadian rhythm disruption are at risk for perinatal depression. This R34 Pilot Effectiveness Studies and Services Research Grant seeks to test whether an Integrated Chronotherapy (IC) intervention can be implemented in an outpatient psychiatry setting to improve treatment outcomes for patients with perinatal depression. IC is a multicomponent treatment consisting of bright light therapy, sleep phase advance, and sleep stabilization/restriction that targets the Research Domain Criteria (RDoC) constructs of circadian rhythms, sleep-wake behavior, social rhythms, and arousal. We will assess the feasibility, safety, and acceptability of an IC intervention for perinatal depressin by testing the treatment in expectant mothers diagnosed with major depressive disorder during 3rd trimester of pregnancy. We will randomize patients to either: (a) usual care (UC, n = 20) or (b) IC+UC (n = 20). IC+UC will have pregnancy and postpartum components and will be administered via an individualized case formulation approach tailored to each patient. After a baseline assessment, IC will be prescribed during 5 dedicated clinical visits: three during 3rd trimester of pregnancy and 2 in the postpartum period. UC will consist of medication administered by a perinatal psychiatrist and/or psychotherapy. UC will be quantified in both groups to evaluate differences between the IC+UC and UC groups. Mood will be measured in both groups by blinded clinician interview and patient self-report. We will assess the safety profile of the IC intervention with evaluation of side effects/adverse events. Importantly, the study will also examine the putative mechanisms by which IC is hypothesized to work and the dose of IC received by patients in the IC+UC group. All participants will wear wrist actigraphy/light monitors continuously during weeks 28-40 of pregnancy and postpartum weeks 2-6 to assess light exposure and sleep duration and timing. Circadian phase (measured with salivary dim light melatonin onset) will be measured at baseline during pregnancy (~30 weeks gestation), at 36 weeks gestation, and at postpartum week 6. This pilot will allow us to refine the IC intervention for future integration into various clinical settings and establish an infrastructue for a larger (R01-scale) trial, including measuring acceptability of IC among UC clinicians and implementing web-based data collection to facilitate data sharing in the planned R01. Perinatal IC could have major public health impact due to the high prevalence of perinatal depression and its negative effects on mothers and their children. This project represents a first step toward achieving this goal, as it will provide the pilot data necessary to prepare for a larger scale intervention study focused on providing non-pharmacologic therapies and improving outcomes for women with perinatal depression.